1. Field of the Invention
The present invention relates to data-entry devices for digital systems.
2. Description of the Prior Art
The prior art, as exemplified in U.S. Pat. Nos. 3,600,528; 3,627,935; 3,641,286; 3,688,066; 3,699,294 and 3,761,944, contains a number of electrical switch devices and mechanisms some of which employ flexible or sheet-like upper conductive members which can be depressed to engage underlying conductive members laid out in patterns or separate contact areas. Prior art entry devices employing upper conductive sheets or metal films overlying contact areas to be selectively engaged are generally deficient in their ability to be employed in digital systems wherein pulses were used to sense the switch operations; modern digital circuitry employs pulses of a frequency and pulse width which are effectively shunted by capacitive coupling in such prior art devices. Additionally, prior art digital entry devices are characterized by one or more deficiencies such as being too complex and costly, being unreliable, requiring excessive time in assembly, etc.